Abstract
BackgroundInclusion of vaccine herd-protection effects in cost-effectiveness analyses (CEAs) can impact the CEAs-conclusions. However, empirical epidemiologic data on the size of herd-protection effects from original studies are limited.MethodsWe performed a quantitative comparative analysis of the impact of herd-protection effects in CEAs for four childhood vaccinations (pneumococcal, meningococcal, rotavirus and influenza). We considered CEAs reporting incremental-cost-effectiveness-ratios (ICERs) (per quality-adjusted-life-years [QALY] gained; per life-years [LY] gained or per disability-adjusted-life-years [DALY] avoided), both with and without herd protection, while keeping all other model parameters stable. We calculated the size of the ICER-differences without vs with-herd-protection and estimated how often inclusion of herd-protection led to crossing of the cost-effectiveness threshold (of an assumed societal-willingness-to-pay) of $50,000 for more-developed countries or X3GDP/capita (WHO-threshold) for less-developed countries.ResultsWe identified 35 CEA studies (20 pneumococcal, 4 meningococcal, 8 rotavirus and 3 influenza vaccines) with 99 ICER-analyses (55 per-QALY, 27 per-LY and 17 per-DALY). The median ICER-absolute differences per QALY, LY and DALY (without minus with herd-protection) were $15,620 (IQR: $877 to $48,376); $54,871 (IQR: $787 to $115,026) and $49 (IQR: $15 to $1,636) respectively. When the target-vaccination strategy was not cost-saving without herd-protection, inclusion of herd-protection always resulted in more favorable results. In CEAs that had ICERs above the cost-effectiveness threshold without herd-protection, inclusion of herd-protection led to crossing of that threshold in 45% of the cases. This impacted only CEAs for more developed countries, as all but one CEAs for less developed countries had ICERs below the WHO-cost-effectiveness threshold even without herd-protection. In several analyses, recommendation for the adoption of the target vaccination strategy depended on the inclusion of the herd protection effect.ConclusionsInclusion of herd-protection effects in CEAs had a substantial impact in the estimated ICERs and made target-vaccination strategies more attractive options in almost half of the cases where ICERs were above the societal-willingness to pay threshold without herd-protection. More empirical epidemiologic data are needed to determine the size of herd-protection effects across diverse settings and also the size of negative vaccine effects, e.g. from serotype substitution.
Highlights
Cost effectiveness analysis (CEA) studies [1] have been increasingly used worldwide and in the US in particular [2,3] for the development of national immunization strategies
We identified 35 CEA studies (20 pneumococcal, 4 meningococcal, 8 rotavirus and 3 influenza vaccines) with 99 incremental cost effectiveness ratios (ICER)-analyses (55 per-quality adjusted life-years gained (QALYs), 27 per-LY and 17 per-DALY)
Vaccine herd-protection has been reported for several childhood vaccinations including pneumococcal (e.g. 7-valent pneumococcal conjugate vaccine (PCV7), PCV10 and PCV13) [13–18] meningococcal, [11,19–21] rotavirus [22,23] and influenza vaccines. [24,25] We evaluated the overall impact of including herd-protection assumptions in CEAs for these four childhood vaccinations
Summary
Cost effectiveness analysis (CEA) studies [1] have been increasingly used worldwide and in the US in particular [2,3] for the development of national immunization strategies. Herd-protection is the reduction of the disease in non-vaccinated susceptible individuals from widespread humoral immunity and/or decreased carriage (e.g. nasopharyngeal carriage) in vaccinated individuals in the community, that lead to decreased likelihood of non-vaccinated individuals having contact with infected/infectious individuals [13]. This phenomenon is widely described, empirical epidemiologic data on the size of indirect vaccine effects are limited. Vaccine CEAs that include indirect vaccine effects in their analyses either use modeling or extrapolate data from studies conducted in other countries, which may have different disease epidemiology. Empirical epidemiologic data on the size of herdprotection effects from original studies are limited
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